s390/purgatory: update .gitignore

Since commit 4c0f032d4963 ("s390/purgatory: Omit use of bin2c"),
kexec-purgatory.c is not generated.

purgatory and purgatory.lds are generated files, so should be ignored
by git.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/arch/s390/purgatory/.gitignore b/arch/s390/purgatory/.gitignore
index e9e66f1..04a0343 100644
--- a/arch/s390/purgatory/.gitignore
+++ b/arch/s390/purgatory/.gitignore
@@ -1,2 +1,3 @@
-kexec-purgatory.c
+purgatory
+purgatory.lds
 purgatory.ro